The electronic control unit stores, as a result of diagnosis, abnormality information, e.g., Diagnostic Trouble Code (DTC), of various diagnosis objects in a rewritable non-volatile memory such as an EEPROM or the like based on information from various sensors installed in the vehicle indicating faulty operation of the diagnosis object.
The electronic control unit having the above-mentioned function may be operated, for example, during a manufacturing process of the vehicle. In such a case, the electronic control unit is operated in a condition that the assembly of the electronic control unit has not yet been complete, that is, in a condition that the apparatus is being operable in the vehicle without the connection of connectors to peripheral devices such as relevant sensors, electronic loads and the like.
Thus, if the electronic control unit is operated to perform diagnosis of peripheral devices, the abnormality is detected by the apparatus, thereby leading to storage of useless abnormality information in the rewritable non-volatile memory.
Therefore, the electronic control unit disclosed in, for example, Japanese patent document JP-A-2006-291730, has a configuration for avoiding storage of the useless abnormality information. That is, the apparatus determines whether or not the vehicle is being used by a user based on a driving condition of the vehicle such as a vehicle speed, an engine rotation or the like, and starts storage of a diagnosis result to a storage unit after determining that the use of the vehicle by the user has been started.
However, the above disclosure uses, as a criterion for starting storage of the diagnosis result, a driving condition that can be assumed as a use of the vehicle by a user and cannot be assumed to be happening in the manufacturing process of the vehicle. Thus, the start of the storage of the diagnosis result may be delayed by a certain period from an actual start of the use of the vehicle by the user.
Therefore, the abnormality information regarding abnormality that has happened relatively immediately after the start of the use of the vehicle by the user, that is, the abnormality information that should be stored, may be prevented from being stored in the rewritable non-volatile memory.